Deposit monitor

ABSTRACT

Fluid flow systems can include one or more resistance temperature detectors (RTDs) in contact with the fluid flowing through the system. One or more RTDs can be operated in a heating mode and a measurement mode. Thermal behavior of the one or more RTDs can be analyzed to characterize a level of deposit formed on the RTD(s) from the fluid flowing through the system. Characterizations of deposition on RTDs operated at different temperatures can be used to establish a temperature-dependent deposition profile. The deposition profile can be used to determine if depositions are likely to form at certain locations in the fluid flow system, such as at a use device. Detected deposit conditions can initiate one or more corrective actions that can be taken to prevent or minimize deposit formation before deposits negatively impact operation of the fluid flow system.

CROSS-REFERENCES

This application is a continuation of U.S. patent application Ser. No.15/262,807 filed Sep. 12, 2016, the content of which is herebyincorporated by reference in its entirety.

BACKGROUND

Various fluid flow systems are arranged to flow a process fluid from oneor more input fluid sources toward a use device. For example, fluidflowing toward a heat exchanger surface can be used to transfer heat toor draw heat from the heat exchange surface and maintain the surface atan operating temperature.

In some examples, changes in the operating conditions of the fluid flowsystem, such as changes in the makeup of the fluid, operatingtemperatures of the fluid or the use device, or the like, can affect thelikelihood of deposits forming from the process fluid onto systemcomponents. Deposits forming on the use device can negatively impact theperformance of the device. For example, deposits forming on the heatexchange surface can act to insulate the heat exchange surface from thefluid, reducing the ability of the fluid to thermally interact with theheat exchanger.

Often, such deposits are detected only when the performance of the usedevice degrades to the point of requiring attention. For example, a heatexchanger surface can become unable to maintain desired temperatures dueto a sufficiently large deposit forming on a heat exchange surfacethereof. In order to restore the system to working order, the systemoften must be shut down, disassembled, and cleaned, which can be acostly and time-consuming process.

SUMMARY

Certain aspects of the disclosure are generally directed to systems andmethods for characterizing levels of deposits and/or detecting depositconditions present in a fluid flow system. Some such systems can includeone or more resistance temperature detectors (RTDs) in thermalcommunication with the fluid flowing through the fluid flow system. TheRTD(s) can interface with a heating circuit configured to applyelectrical power to the RTD(s), for example, to increase the temperatureof the RTD(s). Additionally or alternatively, the RTD(s) can interfacewith a measurement circuit configured to provide an outputrepresentative of the temperature of one or more RTDs.

Systems can include a controller in communication with the heatingcircuit and the measurement circuit, and can be configured to operatethe RTD(s) in a heating mode and a measurement mode. In some examples,the controller can be configured to heat the RTD(s) to an elevatedtemperature (e.g., in the heating mode), stop heating the RTD(s), andcharacterize the temperature change of the RTD(s) over time (e.g., inthe measurement mode). The characterizing the temperature change of theRTD(s) can include characterizing the temperature change due to thermalconduction of heat from the RTD(s) to the fluid flowing through the flowsystem via the measurement circuit. Deposits from the fluid flow on theRTD(s) can impact the thermal conduction between the RTD and the fluid.Thus, in some embodiments, the controller can be configured to determinea level of deposit formed on the surface of the RTD(s) from the fluidbased on the characterized temperature change.

In some examples, a controller can be configured to periodically switchthe RTD(s) between the heating mode and the measurement mode and observechanges in the thermal behavior of the RTD(s). The controller can beconfigured to characterize a level of deposit from the fluid onto theRTD(s) based on the observed changes.

In some exemplary systems including a plurality of RTDs, the controllercan be configured to maintain each of a plurality of RTDs at a differentoperating temperature and perform such processes on the RTDs. Thecontroller can be configured to determine a temperature-dependentdeposition profile based on the characterized levels of deposit of eachof the RTDs and determine, based on the profile, if a deposit conditionexists for the use device.

In various embodiments, observing changes in the behavior of an RTD caninclude a variety of observations. Exemplary observations can includechanges in the temperature achieved by the RTD when a constant power isapplied thereto, changes in the rate of temperature change of the RTD,amount of electrical power applied in the heating mode of operation toachieve a certain temperature, and the like. Each such characteristiccan be affected by deposits forming on the RTD from the fluid, and canbe used to characterize the level of deposit on the RTD.

In some examples, corrective actions can be taken to address detecteddeposits and/or deposit conditions. For example, changes to the fluidflowing through the system can be adjusted to minimize the formation ofdeposits. Such changes can include adding a chemical such as a scaleinhibitor or a biocide to reduce deposit formation or stopping the flowof certain fluids into the system that may be contributing to depositformation. Other corrective actions can include changing systemparameters, such as fluid or use device operating temperatures. In someembodiments, such corrective actions can be performed manually by asystem operator. Additionally or alternatively, such actions can beautomated, for example, via the controller and other equipment, such asone or more pumps, valves, or the like. In still further examples, thesystem can be configured to perform a corrective action in the form ofalerting a user of deposit conditions so that the user can takesubsequent corrective actions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an exemplary placement of one or more RTDsin a fluid flow system.

FIG. 2 is a schematic diagram of a system for operating an RTD in anexemplary embodiment.

FIG. 3 is an exemplary schematic diagram showing an operationalconfiguration of an array of RTDs.

FIG. 4 is a schematic diagram showing operation of a plurality of RTDsin a heating mode of operation.

FIG. 5 is a schematic diagram showing operation of a single of RTDs in ameasurement mode of operation.

FIGS. 6A-6D illustrate exemplary thermal behavior of an RTD that can beused to characterize the level of deposit at the RTD.

FIG. 7 is a process-flow diagram illustrating an exemplary process formitigating deposits from a process fluid onto a use device in a fluidflow system.

DETAILED DESCRIPTION

A resistance temperature detector (RTD) is a device commonly used tomeasure the temperature of an object of interest. For example, in someinstances, the resistance of the RTD is approximately linear withrespect to temperature. The resistance can be measured by passing acurrent through the RTD and measuring the resulting voltage across theRTD. A current flowing through the RTD can have heating effects on theRTD, so the current is typically maintained at a relatively lowmagnitude during a temperature measurement. In exemplary operation, asmall amount of current is passed through a conductor that is exposed tosome environment where temperature is to be measured. As temperaturechanges, the characteristic change in resistance in that conductor(e.g., platinum) is measured and used to calculate the temperature.

FIG. 1 is an illustration of an exemplary placement of one or more RTDsin a fluid flow system. As shown, RTDs 102 a-d are positioned in theflow path 106 of a process fluid in a fluid flow system 100 configuredto direct a process fluid to a use device 105. Arrows 108 illustrate anexemplary flow path of fluid from a fluid source toward the use device105. As described herein process fluids can generally relate to anyfluids flowing through such a fluid flow system, including but notlimited to utility fluids such as cooling water, boiler feed water,condensate, blowdown water, waste water, and discharged effluent water.Such exemplary process fluids can be directed into the fluid flow system100 from a variety of sources (e.g., an effluent stream from a process,boiler blowdown water, treated waste water, produced water, a freshwater source, etc.). In some examples, a single fluid flow system 100can receive input process fluids from a variety of sources. In some suchexamples, the source of process fluid can be selected, such as via amanual and/or automated valve or series of valves. In some embodiments,a single fluid source can be selected from one or more possible inputsources. In alternative embodiments, a plurality of fluid sources can beselected such that fluid from the selected plurality of sources is mixedto form the input fluid. In some implementations, a default input fluidis made up of a mixture of fluids from each of the plurality ofavailable input sources, and the makeup of the input fluid can beadjusted by blocking the flow of one or more such input sources into thesystem.

In the example of FIG. 1, RTDs 102 a-d are shown as an array of RTDsmounted on a sample holder 104. In some examples, sample holder 104 isremovable from the flow path 106 of the fluid flow system 100, forexample, to facilitate cleaning, replacing, or other maintenance of RTDs102 a-d. Additionally or alternatively, one or more RTDs (e.g.positioned on a sample holder) can be positioned in the flow path of oneor more fluid inputs that contribute to the makeup of the fluid flowingthrough the fluid flow system 100 to the use device 105. The fluid flowsystem can be any system in which a process fluid flows, including forexample, washing systems (e.g., warewashing, laundry, etc.), food andbeverage systems, mining, energy systems (e.g., oil wells, refineries,etc.), air flow through engine air intakes, heat exchange systems suchas cooling towers or boilers, pulp and paper processes, and others.Arrows 108 indicate the direction of flow of the fluid past the RTDs102, which can be used to monitor the temperature of the fluid, andtoward the use device 105.

In some embodiments, a fluid flow system comprises one or moreadditional sensors 111 (shown in phantom) capable of determining one ormore parameters of the fluid flowing through the system. In variousembodiments, one or more additional sensors 111 can be configured todetermine flow rate, temperature, pH, alkalinity, conductivity, and/orother fluid parameters, such as the concentration of one or moreconstituents of the process fluid. While shown as being a single elementpositioned downstream of the RTDs 102 a-d, one or more additionalsensors 111 can include any number of individual components, and may bepositioned anywhere in the fluid flow system 100 while sampling the samefluid as RTDs 102 a-d.

FIG. 2 is a schematic diagram of a system for operating an RTD in anexemplary embodiment. In the embodiment of FIG. 2, an RTD 202 is incommunication with a measurement circuit 210. In some examples, themeasurement circuit 210 can facilitate the measurement of the resistanceof the RTD in order to determine the temperature thereof. For instance,in an exemplary embodiment, the measurement circuit can provide acurrent to flow through the RTD and measure the voltage drop across theRTD to determine the resistance, and thus the temperature, thereof.

The system can include a controller 212 in communication with themeasurement circuit 210. The controller 212 can include amicrocontroller, a processor, memory comprising operating/executioninstructions, a field programmable gate array (FPGA), and/or any otherdevice capable of interfacing and interacting with system components. Insome such examples, the system can operate in a measurement mode inwhich the controller 212 can interface with the measurement circuit 210for determining a temperature of the RTD 202. In some examples, thecontroller can cause a current to be applied to the RTD via themeasurement circuit 210, receive a signal from the measurement circuit210 representative of the voltage across the RTD 202, and determine theresistance of the RTD based on the known current and measured voltage.In some embodiments, the controller 212 is configured to otherwisedetermine the resistance and/or the temperature of the RTD 202 based onthe signal received from the measurement circuit. Thus, in some suchexamples, the controller 212 can interface with the measurement circuit210 and the RTD 202 to determine the temperature of the RTD 202.

The system of FIG. 2 further comprises a heating circuit 214 incommunication with the controller 212 and the RTD 202. In some examples,system can operate in a heating mode in which the controller 212 canapply electrical power to the RTD 202 via the heating circuit 214 inorder to elevate the temperature of the RTD 202. In some suchembodiments, the controller 212 is capable of adjusting or otherwisecontrolling the amount of power applied to the RTD 202 in order toelevate the temperature of the RTD 202. In various examples, adjustingthe applied power can include adjusting a current, a voltage, a dutycycle of a pulse-width modulated (PWM) signal, or other known methodsfor adjusting the power applied to the RTD 202.

In some examples, the controller 212 is capable of interfacing with theRTD 202 via the heating circuit 214 and the measurement circuit 210simultaneously. In some such examples, the system can simultaneouslyoperate in heating mode and measurement mode. Similarly, such systemscan operate in the heating mode and in the measurement modeindependently, wherein the RTD may be operated in the heating mode, themeasurement mode, or both simultaneously. In other examples, thecontroller 212 can switch between a heating mode and a measurement modeof operation. Additionally or alternatively, a controller incommunication with a plurality of RTDs 202 via one or more measurementcircuits 210 and one or more heating circuits 214 can operate such RTDsin different modes of operation. In various such examples, thecontroller 212 can operate each RTD in the same mode of operation orseparate modes of operation, and/or may operate each RTD individually,for example, in a sequence. Many implementations are possible and withinthe scope of the present disclosure.

As described with respect to FIG. 1, the system can include one or moreadditional sensors 211 for determining one or more parameters of thefluid flowing through the fluid flow system. Such additional sensors 211can be in wired or wireless communication with the controller 212. Thus,in some embodiments, the controller 212 can be configured to interfacewith both RTDs 202 and additional sensors 211 positioned within thefluid flow system.

FIG. 3 is an exemplary schematic diagram showing an operationalconfiguration of an array of RTDs. In the illustrated embodiment, aseries of RTDs 302 a-d are in communication with a controller 312 via ameasurement circuit 310 and a heating circuit 314. During a heating modeof operation, the controller 312 can cause the heating circuit 314 toprovide electrical power to one or more of the RTDs 302 a-d to elevatethe temperature of the RTD. In the illustrated embodiment, the heatingcircuit 314 includes a PWM module 316 in communication with anamplification stage 318. In the example of FIG. 3, the PWM module 316includes a plurality of channels A-D, each channel corresponding to arespective RTD 302 a-d in the series of RTDs. Each channel of the PWMmodule 316 is in communication with its corresponding RTD 302 a-d viathe amplification stage 318. The amplification stage 318 can beconfigured to modify the signal from the PWM module 316 to generate aheating signal applied to the respective RTD 302 a-d. In some examples,the amplification stage 318 is configured to filter a PWM signal fromthe PWM module 316, for example, via an LRC filter, in order to providea steady power to the RTD 302. Additionally or alternatively, theamplification stage 318 can effectively amplify a signal from the PWMmodule 316 for desirably changing the temperature of the RTD 302.

In an exemplary heating operation embodiment, the controller signals thePWM module 316 to elevate the temperature of an RTD 302 a. Thecontroller 312 can cause the PWM module 316 to output a PWM signal fromchannel A to the amplification stage 318. Aspects of the PWM signal,such as the duty cycle, magnitude, etc. can be adjusted by thecontroller 312 to meet desired heating effects. Additionally oralternatively, the amplification stage 318 can adjust one or moreaspects of channel A of the PWM signal to effectively control the amountof heating of the RTD 302 a. Similar heating operations can be performedfor any or all of RTDs 302 a-d simultaneously. In some embodiments, thecontroller 312 can control heating operation of each of a plurality ofRTDs 302 a-d such that each of the RTDs is elevated to a differentoperating temperature.

As described elsewhere herein, the controller 312 can be capable ofinterfacing with one or more RTDs 302 a-d via a measurement circuit 310.In some such examples, the controller 312 can determine, via themeasurement circuit 310, a measurement of the temperature of the RTD 302a-d. Since the resistance of an RTD is dependent on the temperaturethereof, in some examples, the controller 312 can be configured todetermine the resistance of the RTD 302 a-d and determine thetemperature therefrom. In the illustrated embodiment, the measurementcircuit 310 comprises a current source 330 (e.g., a precision currentsource) capable of providing a desired current through one or more ofthe RTDs 302 a-d to ground 340. In such an embodiment, a measurement ofthe voltage across the RTD 302 a-d can be combined with the knownprecision current flowing therethrough to calculate the resistance, andthus the temperature, of the RTD 302 a-d. In some examples, the currentprovided to the RTDs from the current source 330 is sufficiently small(e.g., in the microamp range) so that the current flowing through theRTD does not substantially change the temperature of the RTD.

In configurations including a plurality of RTDs 302 a-d, the controller312 can interface with each of the RTDs 302 a-d in a variety of ways. Inthe exemplary embodiment of FIG. 3, the measurement circuit 310comprises a multiplexer 320 in communication with the controller 312,the current source 330 and the RTDs 302 a-d. The controller 312 canoperate the multiplexer 320 so that, when a measurement of the voltageacross one of the RTDs (e.g., 302 a) is desired, the multiplexer 320directs the current from the current source 330 through the desired RTD(e.g., 302 a). As shown, the exemplary multiplexer 320 of FIG. 3includes channels A, B, C, and D in communication to RTDs 302 a, 302 b,302 c, and 302 d, respectively. Thus, when measuring the temperature ofa particular one of RTDs 302 a-d, the controller 312 can cause currentto be supplied from the current source 330 and through the appropriatechannel of the multiplexer 320 and through the desired RTD 302 a-d toground 340 in order to cause a voltage drop thereacross.

In order to measure the voltage drop across a desired one of theplurality of RTDs 302 a-d, the measurement circuit 310 includes ademultiplexer 322 having channels A, B, C, and D corresponding to RTDs302 a, 302 b, 302 c, and 302 d, respectively. The controller 312 candirect the demultiplexer 322 to transmit a signal from any one ofrespective channels A-D depending on the desired RTD. The output of thedemultiplexer 322 can be directed to the controller 312 for receivingthe signal indicative of the resistance, and therefore the temperature,of a desired RTD. For example, in some embodiments, the output of thedemultiplexer 322 does not connect or otherwise has high impedance toground. Accordingly, current flowing to an RTD (e.g., 302 a) via arespective multiplexer 320 channel (e.g., channel A) will only flowthrough the RTD. The resulting voltage across the RTD (e.g., 302 a) willsimilarly be present at the respective input channel (e.g., channel A)of the demultiplexer 322, and can be output therefrom for receiving bythe controller 312. In some examples, instead of being directly appliedto controller 312, the voltage across the RTD (e.g., 302 a) at theoutput of the demultiplexer 322 can be applied to a first input of adifferential amplifier 334 for measuring the voltage. The amplifier 334can be used, for example, to compare the voltage at the output of thedemultiplexer 322 to a reference voltage before outputting the resultingamplification to the controller 312. Thus, as described herein, a signaloutput from the demultiplexer 322 for receiving by the controller 312can, but need not be received directly by the controller 312. Rather, insome embodiments, the controller 312 can receive a signal based on thesignal at the output of the demultiplexer 322, such as an output signalfrom the amplifier 334 based on the output signal from the demultiplexer322.

In some examples, the measurement circuit 310 can include a referenceresistor 308 in line between a second current source 332 and ground 340.The current source 332 can provide a constant a known current throughthe reference resistor 308 of a known resistance to ground, causing aconstant voltage drop across the reference resistor 308. The constantvoltage can be calculated based on the known current from the currentsource 332 and the known resistance of the reference resistor 308. Insome examples, the reference resistor 308 is located in a sensor headproximate RTDs 302 a-d and is wired similarly to RTDs 302 a-d. In somesuch embodiments, any unknown voltage drop due to unknown resistance ofwires is for the reference resistor 308 and any RTD 302 a-d isapproximately equal. In the illustrated example, reference resistor 308is coupled on one side to ground 340 and on the other side to a secondinput of the differential amplifier 334. Thus, the current source 332 incombination with the reference resistor 308 can act to provide a knownand constant voltage to the second input of the differential amplifier334 (e.g., due to the reference resistor 308, plus the variable voltagedue to the wiring). Thus, in some such examples, the output ofdifferential amplifier 334 is unaffected by wiring resistance, and canbe fed to the controller 312.

As shown in the illustrated embodiment and described herein, thedifferential amplifier 334 can receive the voltage across the RTD (e.g.,302 a) from the output of the demultiplexer 322 at one input and thereference voltage across the reference resistor 308 at its other input.Accordingly, the output of the differential amplifier 334 is indicativeof the voltage difference between the voltage drop across the RTD andthe known voltage drop across the reference resistor 308. The output ofthe differential amplifier 334 can be received by the controller 312 forultimately determining the temperature of the RTD (e.g., 302 a). It willbe appreciated that, while an exemplary measurement circuit is shown inFIG. 3, measuring the temperature of the RTD could be performed in anyvariety of ways without departing from the scope of this disclosure. Forexample, the voltage drop across the RTD could be received directly bythe controller 312 as an analog input signal. Additionally oralternatively, a relaxation time of an RC circuit having a knowncapacitance, C, and a resistance, R, being the resistance of the RTD canbe used to determine the resistance of the RTD. In some such examples,such a measurement can eliminate any resistance effect of any wireswithout using a reference (e.g., reference resistor 308).

In some embodiments, the controller 312 can operate the multiplexer 320and the demultiplexer 322 in concert so that it is known which of theRTDs is being analyzed. For instance, with respect to the illustrativeexample of FIG. 3, the controller 312 can operate the multiplexer 320and the demultiplexer 322 on channel A so that the current from currentsource 330 flows through the same RTD 302 a that is in communicationwith the differential amplifier 334 via the demultiplexer 322.

In an exemplary configuration such as shown in FIG. 3, in which aplurality of RTDs 302 a-d are in communication with different channelsof the multiplexer 320 and the demultiplexer 322, the controller 312 canact to switch operating channels of the multiplexer 320 anddemultiplexer 322 in order to perform temperature measurements of eachof the RTDs 302 a-d. For instance, in an exemplary embodiment, thecontroller can cycle through respective multiplexer 320 anddemultiplexer 322 channels in order to perform temperature measurementsof each of the respective RTDs 302 a-d.

As described elsewhere herein, in some examples, the controller 312 cancontrol heating operation of one or more RTDs. In some such embodiments,the controller 312 stops heating an RTD prior to measuring thetemperature of the RTD via the multiplexer 320 and demultiplexer 322.Similarly, when heating an RTD via the heating circuit 314, thecontroller 312 can turn off the channel(s) associated with that RTD inthe multiplexer 320 and demultiplexer 322. In some embodiments, for eachindividual RTD, the controller 312 can use the heating circuit 314 andthe measurement circuit 310 (including the multiplexer 320 anddemultiplexer 322) to switch between distinct heating and measurementmodes of operation.

FIG. 4 is a schematic diagram showing operation of a plurality of RTDsin a heating mode of operation. As shown, each of a plurality of RTDs402 a-c is in communication with a respective power source 414 a-c. Asdescribed with reference to FIG. 3, in some examples, each RTD 402 a-cis not affected by any measurement circuit components while operating inthe heating mode. Thus, each RTD 402 a-c can be individually andindependently heated via power sources 414 a-c. While shown as being DCpower sources in the embodiment of FIG. 4, it will be appreciated thatany of a variety of adjustable power sources can be used. In someexamples, the power source 414 a-c comprises a PWM signal filtered andsmoothed to provide a substantially DC signal. While shown as beingseparate power sources 414 a-c, in some embodiments, a single componentcan be used to independently provide adjustable power to each RTD 402a-c.

FIG. 5 is a schematic diagram showing operation of a single of RTDs in ameasurement mode of operation. In the illustrated embodiment, a currentsource 530 is configured to provide a constant current flow through RTD502 to ground 540. The voltage drop across the RTD 502 is applied to afirst input of an amplifier 534. A current source 532 is configured toprovide a constant current flow through a reference resistor 508 toground 540. As described elsewhere herein, the known current from thecurrent source 532 and the known resistance of the reference resistor508 can be used to determine the voltage drop across the referenceresistor 508, which is applied at a second input of the amplifier 534.The output 550 of the amplifier 534 can provide information regardingthe difference between the known voltage drop across the referenceresistor 508 and the voltage drop across the RTD 502, which can be usedto determine the voltage drop across the RTD 502. The determined voltagedrop across the RTD 502 can be used with the known current from currentsource 530 to determine the resistance, and therefore the temperature,of the RTD 502. While not shown in the embodiment of FIG. 5, in someinstances, the RTD 502 is a single RTD selected from an array of RTDs,for example, via the operation of a multiplexer and demultiplexer suchas shown in FIG. 3.

Referring back to FIG. 1, a plurality of RTDs 102 a-d can be disposed inthe flow path of a process fluid in a fluid flow system. In someinstances, the process fluid may include constituents that form deposits(e.g., scale, biofilm, etc.) on various fluid flow system components,such as the walls of the flow path 106, sensors, process instruments(e.g., a use device 105 toward which the process fluid flows), and thelike. In some examples, deposits that form on the RTDs 102 a-d in thefluid flow path can act as an insulating layer between the RTD and theprocess fluid, which can affect the thermal behavior of the RTDs.

Accordingly, in some examples, observing the thermal behavior of one ormore RTDs in the fluid flow path can provide information regarding thelevel of deposit present at the RTDs (e.g., 102 a-d). FIGS. 6A-6Dillustrate exemplary thermal behavior of an RTD that can be used tocharacterize the level of deposit at the RTD.

FIG. 6A shows a plot of temperature and current vs time. In theillustrated example, a high current is applied to an RTD (e.g., asmoothed DC current applied to RTD 302 a via channel A of the heatingcircuit 314 of FIG. 3). The applied current heats the RTD to an elevatedtemperature. At time t₀, the current is reduced, and the temperature ofthe RTD begins to decline. In the illustrated example, the temperatureprofile of both clean (solid line) and fouled (broken line) RTDs areshown. Though each RTD is heated to a high temperature (not necessarilythe same temperature), the clean RTD cools more quickly than the fouled(coated) RTD, since the deposit on the fouled RTD provides thermalinsulation between the RTD and the process fluid. In some embodiments,the temperature decay profile can be analyzed to determine the amount ofdeposit present on the RTD.

With reference to FIG. 2, the controller 212 can heat the RTD 202 viathe heating circuit 214. In some examples, the controller 212 canperiodically switch to measurement mode to measure the temperature ofthe RTD 202 via the measurement circuit 210. At time t₀, the controller212 ceases applying power to the RTD 202 via the heating circuit 214 andswitches to measurement mode to monitor the temperature of the RTD 202via the measurement circuit 210 as the temperature decays due to theprocess fluid. The decay profile of the temperature of the RTD 202 canbe monitored by the controller 212 via the measurement circuit 210. Insome examples, the controller 212 is configured to analyze thetemperature decay profile to determine the level of deposit on the RTD202. For instance, the controller 212 can fit the decay profile to afunction such as an exponential function having a time constant. In somesuch examples, the fitting parameters can be used to determine the levelof deposit.

In an exemplary embodiment, the temperature decay profile over time canbe fit to a double exponential function. For example, in some instances,a first portion of the double exponential decay model can representtemperature change due to the process fluid flowing through the flowsystem. A second portion of the double exponential decay model canrepresent temperature conductivity from a heated RTD to othercomponents, such as wires, a sample holder (e.g., 104 in FIG. 1) orother components. In some such embodiments, the double exponentialfitting functions can independently represent both sources oftemperature conduction in the same function, and can be weighted toreflect the relative amount and timing of such temperature changes. Insome such examples, a fitting parameter in the first portion of thedouble exponential decay model is representative of the level of depositon the surface of an RTD interfacing with the fluid. Thus, in some suchembodiments, the second portion of the exponential does not contributeto the characterized level of deposit. It will be appreciated that otherfitting functions can be used in addition or alternatively to such adouble exponential function.

In some cases, using certain fitting functions in characterizing thedeposit can be skewed if the RTD is allowed to reach equilibrium withthe process fluid, after which it stops changing in temperature.Accordingly, in various embodiments, the controller 212 is configured toresume heating the RTD prior to the RTD reaching thermal equilibriumand/or to stop associating collected temperature data with the thermaldecay profile of the RTD prior to the RTD reaching equilibrium with theprocess fluid. Doing so prevents non-decay data from undesirablyaltering the analysis of the thermal decay profile of the RTD. In otherembodiments, the fitting function can account for equilibration of theRTD temperature and the process fluid temperature without skewing thefitting function. In some such embodiment, the type of fitting functionand/or weighting factors in the fitting function can be used to accountfor such temperature equilibration.

In some embodiments, the difference in decay profiles between clean andfouled RTDs can be used to determine the level of deposit on the fouledRTD. The decay profile of the clean RTD can be recalled from memory ordetermined from an RTD known to be free from deposit. In some instances,a fitting parameter such as a time constant can betemperature-independent. Thus, in some such embodiments, it is notnecessary that the clean and fouled RTD are elevated to the sametemperature for comparing aspects of their thermal decay profiles.

FIG. 6B shows a plot of temperature vs. time. In the illustratedexample, an RTD is heated from a steady state condition (e.g., thermalequilibrium with the process fluid) while the temperature is monitored.As opposed to the temperature monitoring of FIG. 6A, in which thetemperature can be continuously monitored since the temperature isdecaying from an elevated temperature, monitoring the temperature of theRTD while increasing the temperature as in FIG. 6B requires heating ofthe RTD. Accordingly, in some embodiments, in order to achieve a plotsuch as that shown in FIG. 6B, the RTD can be rapidly switched from theheating mode to the measurement mode and back to the heating mode inorder to achieve a nearly instantaneous temperature measurement whilethe temperature of the RTD does not significantly change due to theprocess fluid. In such a procedure, the temperature of the RTD can beelevated via the heating circuit and periodically sampled via themeasurement circuit in order to determine a heating profile of the RTDover time.

Similar to FIG. 6A discussed above, the plot of FIG. 6B includes twocurves—one representative of a clean RTD (solid line) and onerepresentative of a fouled RTD (broken line). As shown, the fouled RTDincreases in temperature much more quickly than the clean RTD, since thedeposit on the fouled RTD insulates the RTD from the cooling effects ofthe process fluid. Thus, in some examples, the heating profile of theRTD can be used to determine a level of deposit on the RTD, for example,by fitting the heating profile to a function.

In some embodiments, rather than observing properties regarding RTDtemperature change, an RTD can be raised to a fixed operatingtemperature. FIG. 6C shows a plot of the power required to maintain anRTD at a constant temperature over time. As shown, the power required tomaintain a clean RTD (solid line) at a constant temperature remainsrelatively constant over time, as the RTD and process fluid reach anequilibrium condition. However, if deposits form on the RTD over time(as shown in the broken line representing a fouled RTD), the insulatingproperties of the deposit shield the RTD from the cooling effects of theprocess fluid. Thus, as the deposit forms over time, less power isrequired to be applied to the RTD in order to maintain a constanttemperature.

With reference to FIG. 3, in some embodiments, the controller 312 isconfigured to heat an RTD (e.g., 302 a) via the heating circuit 314. Thecontroller 312 can periodically measure the temperature of the RTD(e.g., 302 a) via the measurement circuit 310 as a way of providingfeedback for the heating circuit 314 operation. That is, the controller312 can determine the temperature of the RTD (e.g., 302 a) via themeasurement circuit and adjust the power applied to the RTD (e.g., 302a) via the heating circuit 314 accordingly to achieve and maintain adesired temperature at the RTD. In some such embodiments, the controllerswitches between the heating mode to the measurement mode and backrapidly so that the temperature of the RTD does not significantly changewhile measuring the temperature. In various examples, the controller 312can determine how much power is being applied to the RTD (e.g., 302 a),for example, via a magnitude, duty cycle, or other parameter appliedfrom one or more components of the heating circuit 314 (e.g., the PWMmodule 316 and/or the amplification stage 318) controlled by thecontroller 312.

In some examples, the amount of power required to maintain the RTD at afixed temperature is compared to the power required to maintain a cleanRTD at the fixed temperature. The comparison can be used to determinethe level of deposit on the RTD. Additionally or alternatively, theprofile of the required power to maintain the RTD at the fixedtemperature over time can be used to determine the level of deposit onthe RTD. For instance, the rate of change in the power required tomaintain the RTD at the fixed temperature can be indicative of the rateof deposition of the deposit, which can be used to determine the levelof a deposit after a certain amount of time.

In another embodiment, an RTD can be operated in the heating mode byapplying a constant amount of power to the RTD via the heating circuitand observing the resulting temperature of the RTD. For instance, duringexemplary operation, the controller can provide a constant power to anRTD via the heating circuit and periodically measure the temperature ofthe RTD via the measurement circuit. The switching from the heating mode(applying constant power) to the measurement mode (to measure thetemperature) and back to the heating mode (applying constant power) canbe performed rapidly so that the temperature of the RTD does notsignificantly change during the temperature measurement.

FIG. 6D is a plot of temperature vs time of an RTD to which a constantpower is applied via a heating circuit. In the event of a clean RTD(solid line), the resulting temperature from the applied constant poweris approximately constant over time. However, the temperature of afouled RTD (broken line) increases over time. As described elsewhereherein, as deposits form on the RTD, the deposits insulate the RTD fromthe cooling effects of the process fluid. In general, a thicker depositwill result in greater insulating properties, and thus a greatertemperature achieved by applying the same power to the RTD.

In some embodiments, the difference in temperature between a clean RTDand an RTD under test when a constant power is applied to each can beused to determine the level of deposit on the RTD under test.Additionally or alternatively, the rate of temperature increase based ona constant applied power can provide information regarding the rate ofdeposition of a deposit on an RTD, which can be used to determine alevel of deposit on the RTD.

With reference to FIGS. 6A-6D, various processes have been described forcharacterizing a deposit on an RTD. Such processes generally involveheating the RTD via a heating circuit and measuring a temperature of theRTD via a measurement circuit. Changes in the thermal behavior of theRTD (e.g., temperature increase or decay profile, the applied powerrequired to reach a predetermined temperature, the temperature achievedat a predetermined applied power) provide evidence of a deposit formingon the RTD. In some examples, such changes can be used to determine alevel of deposit on the RTD.

In various embodiments, a controller can be configured to interface witha heating circuit and a measurement circuit in order to perform one ormore of such processes to observe or detect any deposition from aprocess fluid onto an RTD. In an exemplary implementation with referenceto FIGS. 1 and 2, an RTD (e.g., 102 a) can be elevated to the operatingtemperature of a use device 105 via a heating circuit (e.g., 214). Sincethe deposition of constituents of a process fluid is often temperaturedependent, elevating the temperature of the RTD to the operatingtemperature of the use device can simulate the surface of the use deviceat the RTD. Accordingly, deposits detected at the RTD can be used toestimate deposits at the use device.

In some examples, the use device becomes less functional when depositsare present. For instance, in a heat exchanger system wherein the usedevice comprises a heat exchange surface, deposits formed on the heatexchange surface can negatively impact the ability for the heat exchangesurface to transfer heat. Accordingly, sufficient depots detected at theRTD can alert a system operator of likely deposits at the heat exchangesurface, and corrective action can be taken (e.g., cleaning the heatexchange surface). However, even if the RTD simulating the use deviceallows a system operator to detect the presence of a deposit at the usedevice, addressing the detected deposit (e.g., cleaning, etc.) canrequire costly system downtime and maintenance since the deposition hasalready occurred. Additionally or alternatively, in some instances,various deposits may not clean well even if removed for a cleaningprocess, possibly rendering the use device less effective.

Accordingly, in some embodiments, a plurality of RTDs (e.g., 102 a-d)can be disposed in a single fluid flow path (e.g., 106) and used tocharacterize the status of the process fluid and/or the fluid flowsystem (e.g., 100). With reference to FIG. 1, in an exemplaryimplementation, use device 105 of the fluid flow system 100 typicallyoperates at operating temperature T₀. RTDs 102 a-d can be elevated totemperatures more likely to drive deposition of a deposit from theprocess fluid than T₀. For example, various process fluids can includeconstituents such as calcium and/or magnesium sulfates, carbonates,and/or silicates, and/or other components that can be deposited from theprocess fluid. Some such process fluids are more prone to producedeposits on higher temperature surfaces when compared to lowertemperatures. In some such examples, one or more of the plurality ofRTDs 102 a-d are elevated to a temperature higher than the typicaloperating temperature of the use device 105 in order to induce depositsonto the RTDs and to characterize the deposits forming on the RTDs. Thisalso can represent a “worst case” for use device 105 operation whendeposit formation is more likely than usual, such as at an unusuallyhigh temperature.

For example, with reference to FIG. 3, in an exemplary embodiment, eachof RTDs 302 a-d is heated to a different elevated characterizationtemperature via channels A-D, respectively, of the heating circuit 314.In the exemplary embodiment, the characterization temperature of each ofthe RTDs 302 a-d is above a typical operating temperature of a usedevice of the fluid flow system. In some such examples, the controller312 controls the heating circuit 314 to maintain the RTDs 302 a-d attheir respective elevated characterization temperatures. The controller312 can periodically switch to operate RTDs 302 a-d in a measurementmode via the measurement circuit 310 (e.g., using multiplexer 320 anddemultiplexer 322 and current sources 330, 332) to ensure the RTDs 302a-d are elevated to the desired characterization temperature.

During operation, after maintaining the RTDs 302 a-d at their respectivecharacterization temperatures, the controller 312 can be configured toperform a deposit characterization process such as those described abovewith respect to any of FIGS. 6A-D. For example, the controller 312 can,after operating an RTD in the heating mode to maintain an elevatedtemperature, periodically switch between the heating mode andmeasurement mode and observe changes in the thermal behavior of the RTD.As described with respect to FIGS. 6A-D, periodically switching betweenthe heating mode and the measurement mode can be performed in a varietyof ways.

For example, such switching can include switching to a measurement modefor a period of time to observe the temperature decay of the RTD (e.g.,as in FIG. 6A) before heating again. Changes in the thermal behavior ofthe RTD can include a change in time constant demonstrated by thetemperature decay. Alternatively, periodically switching between theheating mode and the measurement mode can include increasing thetemperature of the RTD while rapidly switching to the measurement modeto sample the temperature of the RTD and back to the heating mode tocontinue heating (e.g., as in FIG. 6B). Similarly, changes in thethermal behavior of the RTD can include changes in a time constantdemonstrated in the temperature increase profile.

In still another example, periodically switching between the heatingmode and the measurement mode can include heating the RTD to maintainthe RTD at a constant temperature while periodically switching to themeasurement mode to confirm the constant temperature is maintained(e.g., as illustrated in FIG. 6C). In such an embodiment, changes inthermal behavior of the RTD can include changes in the amount of powerapplied by the heating circuit to maintain the temperature of the RTD atthe constant temperature. Alternatively, periodically switching betweenthe heating mode and the measurement mode can include heating the RTDusing a constant applied power while periodically sampling thetemperature of the RTD in the measurement mode (e.g., as illustrated inFIG. 6D). In such an embodiment, changes in the thermal behavior of theRTD can include changes in the temperature achieved by the RTD due tothe constant applied amount of power.

As discussed elsewhere herein, observing such changes in the thermalbehavior of an RTD can be indicative of, and used to determine, a levelof deposit on the RTD. Thus, in some examples, the controller 312 canperform any of such processes on the plurality of RTDs 302 a-d that havebeen elevated to different temperatures to characterize the level ofdeposit on each of the RTDs 302 a-d. In some such examples, thecontroller 312 characterizes the deposit level at each of the RTDs 302a-d individually via corresponding channels A-D in the multiplexer 320and demultiplexer 322.

The controller 312 can be configured to associate the level of depositof each RTD with its corresponding characterization temperature. Thatis, the controller 312 can determine a level of deposit at each of theRTDs 302 a-d and associate the level of deposit with the initialcharacterization temperature of each of the respective RTDs 302 a-d. Theassociated deposit levels and operating temperatures can be used tocharacterize a temperature dependence of deposition on surfaces in thefluid flow system. If the typical operating temperature of the usedevice (e.g., a heat exchanger surface) is lower than thecharacterization temperatures of the RTDs 302 a-d, and deposits aredriven by increased temperature, the use device will tend to have lessdeposit than the RTDs 302 a-d. Moreover, the temperature dependence ofdeposition characterized by the RTD operation can be used to infer thelikelihood of deposits forming on the use device.

Additionally or alternatively, periodically observing the depositions onthe various RTDs operating at different characterization temperaturescan provide information regarding general increases or decreases in theoccurrence of depositions. Such changes in deposition characteristics ofthe process fluid can be due to a variety of factors affecting the fluidflow system, such as a change in the temperature or concentration ofconstituents in the process fluid.

In an exemplary operation, an increase in deposition and/or depositionrate detected from the characterization RTDs can be indicative of adeposit condition for the use device, in which deposits forming on theuse device during normal operation become more likely. The detection ofa deposit condition can initiate subsequent analysis to determine thecause of increased deposition, such as measuring one or more parametersof the process fluid. In some instances, this can be performedautomatically, for example, by the controller.

Additionally or alternatively, one or more parameters of the processfluid can be adjusted to reduce the deposits deposited from the processfluid into the fluid flow system and/or to eliminate the deposits thathave already accumulated. For instance, a detected increase indeposition can cause an acid or other cleaning chemical to be releasedto attempt to remove the deposit. Similarly, in some examples, achemical such as an acid, a scale inhibitor chemical, a scaledispersant, a biocide (e.g., bleach), or the like can be added to theprocess fluid to reduce the likelihood of further deposition.

In some examples, an increase in deposition (e.g., scale) over time canbe due to the absence of or reduction in a typical process fluidconstituent (e.g., a scale inhibitor and/or a scale dispersant), forexample, due to equipment malfunction or depletion of a chemical.Reintroducing the constituent into the process fluid can act to reducethe amount of deposition from the process fluid into the fluid flowsystem. Additionally or alternatively, various fluid properties that canimpact the likelihood of deposit formation can be measured via one ormore sensors (e.g., 111) in the fluid flow system, such as fluidoperating temperature, pH, alkalinity, and the like. Adjusting suchfactors can help to reduce the amount and/or likelihood of deposition.

In various embodiments, any number of steps can be taken in response toaddress an increase in detected deposition or other observed depositiontrends. In some embodiments, the controller is configured to alert auser of changes or trends in deposits. For example, in variousembodiments, the controller can alert a user if deposit rates, levels,and/or changes therein meet a certain criteria. In some such examples,criteria can be temperature dependent (e.g., a deposit level or rateoccurring at an RTD with a certain characterization temperature) ortemperature independent. Additionally or alternatively, the controllercan alert a user if determined properties of the process fluid satisfycertain criteria, such as too low or too high of a concentration of afluid constituent (e.g., that increase or decrease likelihood ofdeposits) and/or various fluid properties that may impact the amountand/or likelihood of deposition.

In some such examples, alerting the user is performed when the system ispotentially trending toward an environment in which deposits may beingto form on the use device so that corrective and/or preventative actioncan be taken before significant deposits form on the use device. In someexamples, an alert to a user can include additional information, such asinformation regarding properties of the process fluid flowing throughthe system, to better help the user take appropriate action.Additionally or alternatively, in some embodiments, the controller canbe configured to interface with other equipment (e.g., pumps, valves,etc.) in order to perform such action automatically.

In some systems, certain deposits become more likely as the depositsurface temperature increases. Thus, in some embodiments, RTDs (e.g.,302 a-d) can be heated to temperatures above the typical operatingtemperatures of a use device in order to intentionally induce andmonitor deposits from the process fluid can help to determine situationsin which the use device is at risk for undesired deposits. In some suchembodiments, observing deposition characteristics on one or more RTDsthat are operating at a temperature higher than a typical temperature ofthe use device can be used to determine deposition trends or events atcertain surface temperature while minimizing the risk of actualdeposition on the use device. In some instances, elevating differentRTDs to different temperature provides the controller with informationregarding the temperature dependence of deposit formation in the fluidflow system, and can be further used to characterize deposit formationin the fluid flow system.

After repeated or prolonged characterization in which the RTDs areheated to induce deposits, the RTDs may eventually become too coated foreffective characterization. In some such embodiments, the plurality ofRTDs (e.g., 102 a-d) can be removed from the system and cleaned orreplaced without disrupting operation of the system or use device. Forexample, with reference to FIG. 1, the RTDs 102 a-d can be mounted to asample holder 104 that is easily removable from the system 100 forservicing the RTDs 102 a-d. Thus, in some embodiments, cleaning orreplacing the characterization RTDs can be performed with much lowercost and less downtime than having to service the use device itself.

In some examples, the likelihood of deposits forming within a fluid flowsystem can be considered a deposit potential of the system. In variousembodiments, the deposit potential can be a function of surfacetemperature of an object within the fluid flow system. In otherexamples, the deposit potential may be associated with a particular usedevice within the system. In some systems, the deposit potential can beused as a metric for observing the absolute likelihood of depositsforming within the system. Additionally or alternatively, the depositpotential can be used as a metric for observing change in the depositconditions within the fluid flow system. In some such examples, theabsolute deposit potential need not necessarily correspond to a depositcondition, but changes in the deposit potential may be indicative ofincreased likelihood of a deposit condition, for example.

FIG. 7 is a process-flow diagram illustrating an exemplary process forassessing the deposit potential of a process fluid onto a use device ina fluid flow system. The method includes bringing one or more RTD(s) toa unique characterization temperature (760) and maintaining the RTD(s)at the characterization temperatures to drive deposits from the processfluid onto the RTD(s) (762). This can be performed, for example, byoperating the RTD(s) in a heating mode using a heating circuit asdescribed elsewhere herein. In some examples, at least one of thecharacterization temperatures is higher than an operating temperature ofthe use device. It will be appreciated that, bringing one or more RTD(s)to a characterization temperature can include operating one or moreRTD(s) in thermal equilibrium with the process fluid flowing through thefluid flow system. That is, the characterization temperature for one ormore RTDs can be approximately the same temperature as the process fluidflowing through the fluid flow system.

The method further includes periodically switching the RTD(s) from theheating mode to a measurement mode to measure the temperature of theRTD(s) (764) and observing changes in the thermal behavior of the RTD(s)(766). This can include, for example, processes as described withrespect to FIGS. 6A-D. The observed changes can be used to characterizea level of deposit from the process fluid onto each of the one or moreRTD(s) (768). This can include, for example, determining a time constantfor a fitting function of measured temperature decay and observingchanges to the time constant at different measurement times. Changes inthe time constant can be representative of deposits forming on the RTDand altering the thermal behavior of the RTD. In some examples,characterizing the level of deposit can include comparing decay profilesfor RTDs operating at difference characterization temperatures (e.g., aheated RTD and an unheated RTD).

In addition to a deposit thickness, additional characterization of thelevels of deposit can include determining a likely deposited material inthe system. Comparing the thermal decay profiles for heated and unheatedor only slightly heated RTDs, the nature of the deposit can bedetermined. For example, in some cases, sedimentation and/or biofilm(e.g., microbial growth) deposits are generally unaffected by thesurface temperature, while scaling effects will be enhanced at highertemperatures. Thus, the characterization temperature dependence of thethermal decay profiles can be used to characterize the type of depositspresent at the RTDs and within the fluid flow system.

The method can further include determining if a deposit condition existsat the use device. This can include, for example, monitoring thedeposition levels and/or rates at the plurality of RTD(s) over time toobserve deposition trends. In some examples, certain rates of depositionor increases in rates of deposition can indicate a deposit condition inwhich deposits forming on the use device become more likely. In somesuch examples, levels of deposit, rates of deposit, and/or changestherein at an RTD can be analyzed in combination with its associatedcharacterization temperature to determine if a deposit condition exists.Additionally or alternatively, analyzing the relationship of such data(e.g., levels of deposit, rates of deposit, and/or changes therein) withrespect to temperature (e.g., at RTD(s) having differencecharacterization temperatures) can be used to detect a depositcondition.

In some examples, monitored deposit levels, deposit rates, and/or otherdata such as fluid properties (e.g., temperature, constituentconcentrations, pH, etc.) can be used to determine a deposit potentialof the process fluid on to the use device. In various embodiments, thedeposit potential meeting a predetermined threshold and/or changing by apredetermined amount can be used to detect the presence of a depositcondition.

In the event of a deposit condition, the method can include takingcorrective action to address the deposit condition (772). The correctiveaction can include a variety of actions, such as introducing or changingthe dose of one or more chemicals in the process fluid, changing thetemperature of the process fluid, alerting a user, adjusting the usedevice for the process fluid (e.g., a heat load on a heat exchanger),increasing a rate of blowdown, and/or other actions that can affect thedeposition characteristics of the process fluid. In an exemplaryembodiment, deposition characterization can include determining thelikely deposited material, such as scale, biofilm, or the like.

In some such embodiments, the corrective action (e.g., 772) can bespecifically taken to address the determined deposit material. Forinstance, a scale inhibitor can be added or increased due to a detectedscaling event. However, if the deposition characterization isrepresentative of a biofilm rather than scale, a biocide can be added orincreased. Such corrective actions can be performed automatically by thesystem. Additionally or alternatively, the system can signal to a userto take corrective action to address the deposit condition.

In some embodiments in which the fluid flow system can receive fluidfrom a plurality of fluid sources (e.g., selectable input sources), thecorrective action can include changing the source of fluid input intothe system. For instance, in an exemplary embodiment, a fluid flowsystem can selectively receive an input fluid from a fresh water sourceand from an effluent stream from another process. The system caninitially operate by receiving process fluid from the effluent stream.However, in the event of a detected or potential deposit condition, thesource of fluid can be switched to the fresh water source to reduce thepossible deposit materials present in the process fluid. Switching thesource of fluid can include completely ceasing the flow of fluid fromone source and starting the flow of fluid from a different source.Additionally or alternatively, switching sources can include a mixtureof the original source (e.g., the effluent stream) and the new source(s)(e.g., the fresh water). For example, in some embodiments, a desiredblend of fluid from different input sources (e.g., 50% from one sourceand 50% from another source) can be selected.

In a similar implementation, in some embodiments, the corrective actioncan include temporarily stopping flow from a single source (e.g., aneffluent source) and providing a process fluid from a different source(e.g., fresh water). The new source of fluid can be used temporarily toflush potential deposit materials from the system before excessivedeposit can occur. In some examples, once such materials have beenflushed from the system (e.g., via fresh water), the source of theprocess fluid can be switched back to the original source (e.g., theeffluent stream). In some examples, flushing the fluid from the systemcan be done while operating the use device in the system. In otherexamples, when certain deposit conditions and/or likelihoods aredetected (e.g., a certain deposit potential is reached), flow to the usedevice can be stopped and the fluid in the system can be directed to adrain to rid the system of such fluid. The system can then direct fluidback to the use device from either fluid source or a combinationthereof.

In still another implementation, as described elsewhere herein, adefault input fluid can be the combined flow of fluid from each of aplurality of available sources. In the event of detected depositconditions, one or more of the fluid sources can be closed off from thesystem (e.g., via a shutoff valve). In some examples, systems caninclude one or more auxiliary sensors configured to monitor one or moreparameters of the fluid flowing into the system from each input source,such as a conductivity sensor, concentration sensor, turbidity sensor,or the like. Data from such auxiliary sensors can be used to determinewhich of the input sources is/are contributing to the deposit condition.Such fluid sources can then be prevented from contributing to the fluidflowing through the system.

Blocking, switching between, and/or combining process fluid inputsources can be performed, for example, via one or more valves arrangedbetween the source(s) and the fluid flow system. In various embodiments,the valves can be manually and/or automatically controlled to adjust thesource(s) of the input fluid. For example, in some embodiments, adetected deposit condition can cause a controller in communication withone or more such valves to actuate such valves to adjust the source offluid flowing into the system. Alternatively, the controller canindicate to the user that corrective action should be performed, and theuser can actuate such valves to adjust the source of fluid to thesystem.

As described elsewhere herein, one or more fluid input sources caninclude one or more RTDs disposed therein. Such RTD(s) can be used tocharacterize deposit conditions for each of the plurality of fluidsources individually. Accordingly, if one fluid source is exhibiting adeposit condition, one or more corrective actions can include performingan action to affect the fluid flowing into the system from that source(e.g., adjusting a parameter of the fluid) and/or blocking the fluidfrom flowing into the system (e.g., via a valve). In some examples, eachinput fluid source includes one or more such RTDs so that each sourcecan be characterized individually. In some such embodiments, one or moreRTDs can additionally be positioned in the fluid flow path after fluidfrom each of the fluid sources are combined so that the composite fluidcan also be characterized separately from each of the individualsources.

In general, taking one or more corrective actions (e.g., step 772) canact to reduce the rate of deposition at the use device. Thus, in somesuch embodiments, the corrective action acts as a preventative actionfor preventing undesirable deposits from forming on the use device. Thiscan prolong the operability of the use device while minimizing oreliminating the need to shut down the system in order to clean depositsfrom the use device.

In some embodiments the taken and/or suggested corrective action can bebased on data received from one or more additional sensors (e.g., 111).For instance, in some embodiments, reduction in a scale inhibitor (e.g.,detected via a scale inhibitor introduction flow rate meter and/or ascale inhibitor concentration meter) contributes to a deposit conditionin the system. Thus, the corrective action can include replenishing asupply of scale inhibitor. Similarly, in some examples, the presence ofexcess deposit material (e.g., calcium detected by a concentrationmeter) contributes to a deposit condition. Corresponding correctiveaction can include introducing or increasing the amount of a scaleinhibitor into the system. Additionally or alternatively, a correctiveaction can include changing phosphate levels in the fluid. For example,phosphate deposits accumulating in the system can result in reducing theflow of a phosphorus-containing chemical or phosphate depositioncatalyst. In other examples, the addition of phosphate-containing fluidsmay inhibit other deposits from forming. In some such examples, suchphosphate- or phosphorus-containing fluids can be added or increased.

Appropriate corrective actions can be determined, in some embodiments,based on the characterized levels of deposits (e.g., at step 768). Forexample, greater deposition rates and/or deposit potentials can resultin greater amounts of scale inhibitor to be released into the system toprevent deposits from forming. Additionally or alternatively,characterizations in the type of deposits forming (e.g., by comparingthermal decay profiles at different temperatures) can influence whichcorrective actions are taken. For example, if characterization of thedeposit levels indicates that the deposits are generally sedimentationrather than scaling, releasing scale inhibitor chemicals may not be auseful action, and other, more appropriate action may be taken.

Various embodiments have been described. Such examples are non-limiting,and do not define or limit the scope of the invention in any way.Rather, these and other examples are within the scope of the followingclaims.

1. A method for characterizing the level of deposits from a fluid in afluid flow system comprising: operating a resistance temperaturedetector (RTD) in a heating mode of operation in order to heat the RTDand induce a deposit from the fluid to form on a surface of the RTD influid communication with the fluid; periodically switching the RTDbetween the heating mode and a measurement mode in order to measure thetemperature of the RTD, observing changes in the thermal behavior of theRTD in one or both of the heating mode and the measurement mode, andcharacterizing a level of deposit from the process fluid onto the RTDbased on the observed changes.
 2. The method of claim 1, whereinobserving changes in the thermal behavior of the RTD comprises, afteroperating the RTD in the heating mode, switching the RTD to operate inthe measurement mode and measuring the rate at which the temperature ofthe RTD changes; and wherein characterizing the level of deposit fromthe process fluid onto the RTD comprises associating the rate thetemperature of the RTD decreases with a level of deposit from theprocess fluid.
 3. The method of claim 1, wherein: operating the RTD inthe heating mode comprises operating the RTD at a fixed operating power;periodically switching between the heating mode and the measurement modefurther comprises switching from the heating mode to the measurementmode, measuring the temperature of the RTD, and switching back to theheating mode; observing changes in the behavior of the RTD comprisesobserving the change in temperature over time while operating the RTD atthe fixed operating power; and characterizing a level of deposit fromthe process fluid comprises associating the rate of change intemperature of the RTD at the fixed operating power with a level ofdeposit from the process fluid.
 4. The method of claim 1, wherein:operating the RTD in a heating mode of operation comprises elevating theRTD to a fixed temperature; periodically switching between the heatingmode and the measurement mode further comprises switching from theheating mode to the measurement mode to confirm the temperature of theRTD is the fixed temperature; observing changes in the behavior of theRTD comprises observing a change in the electrical power required toelevate the RTD to the fixed temperature; and characterizing the levelof deposit from the process fluid comprises associating the rate ofchange of applied power required to elevate the RTD to the fixedtemperature with a level of deposit from the process fluid.
 5. Themethod of claim 4, wherein the fixed elevated temperature corresponds toan operating temperature of equipment in the process fluid flow path. 6.The method of claim 1, wherein periodically switching between theheating mode and the measurement mode comprises rapidly switching fromthe heating mode to the measurement mode and back to the heating mode sothat, while in the measurement mode, the temperature of the RTD does notsignificantly change; observing changes in the behavior of the RTDcomprises measuring the rate at which the temperature of the RTDincreases due to the operating the RTD in the heating mode; andcharacterizing the level of deposit from the process fluid onto the RTDcomprises associating the rate the temperature of the RTD rises with alevel of deposit from the process fluid.
 7. The method of claim 1,further comprising, if the characterized level of deposit meets apredetermined condition, performing a corrective action.
 8. The methodof claim 7, wherein the corrective action comprises one or more actionsfrom the group consisting of: adding a chemical to the fluid, changingthe dose of a chemical in the fluid, stopping the flow of a fluid fromone or more fluid sources, increasing the rate of blowdown, changing thetemperature of the process fluid, adjusting a use device toward with theprocess fluid flows, and alerting a user.
 9. A fluid flow system fordirecting a fluid toward a use device comprising: a plurality ofresistance temperature detectors (RTDs); a heating circuit in electricalcommunication with the plurality of RTDs and capable of applyingelectrical power to the RTDs; a measurement circuit in communicationwith the plurality of RTDs; a controller in communication with theheating circuit and the measurement circuit and capable of operatingeach of the plurality of RTDs in a heating mode via the heating circuitand a measurement mode via the measurement circuit, the controller beingconfigured to: operate one or more of the plurality of RTDs in theheating mode of operation in order to maintain each of the one or moreRTDs at a characterization temperature to induce a deposit from theprocess fluid to form on at least one of the one or more RTDs, at leastone of the characterization temperatures being higher than a typicaloperating temperature of the use device; for each of the one or moreRTDs, periodically switch the RTD between the heating mode and themeasurement mode in order to measure the temperature of the RTD, observechanges in the thermal behavior of the RTD in one or both of the heatingmode and the measurement mode, and characterize a level of deposit fromthe process fluid onto the RTD based on the observed changes; determinea temperature-dependent deposition profile based on the characterizedlevel of deposit of each of the one or more RTDs; and determine if adeposit condition exists for the use device based on the depositionprofile.
 10. The system of claim 9, wherein, if it is determined that adeposit condition exists for the use device, performing one or morecorrective actions to address the deposit condition.
 11. The system ofclaim 10, wherein at least one of the one or more corrective actions areselected from the group consisting of: introducing a chemical into thefluid, changing the amount of a chemical added to the fluid, changingthe temperature of the fluid, alerting a user of a deposit condition,adjusting one or more operating conditions of the use device, andincreasing the rate of blowdown of the system.
 12. The system of claim10, further comprising an input to the fluid flow system in selectivefluid communication with a plurality of fluid sources; and wherein theone or more corrective actions comprises adjusting the source of fluidto the system.
 13. The system of claim 12, wherein adjusting the sourceof the fluid to the system comprises stopping the flow of a fluid fromone or more of the plurality of fluid sources.
 14. The system of claim9, wherein the controller is further configured to determine a criticaltemperature associated with the formation of a deposit on the RTD fromthe process fluid.
 15. A deposit analysis system comprising: at leastone resistance temperature detector (RTD) positioned in a fluid flowsystem such that a surface of the at least one RTD is in thermalcommunication with the fluid flowing through the fluid flow system; aheating circuit in communication with the at least one RTD and beingconfigured to apply a variable amount of electrical power to the RTD inorder to affect the temperature thereof; a measurement circuit incommunication with the at least one RTD and being configured to output asignal representative of the temperature thereof; and a controller incommunication with the heating circuit and the measurement circuit andconfigured to: heat the at least one RTD to an elevated temperature viathe heating circuit; stop heating the at least one RTD; characterize thetemperature change of the at least one RTD over time due to thermalconduction of heat from the at least one RTD to the fluid flowingthrough the fluid flow system via the measurement circuit; and determinea level of deposit formed on the surface of the at least one RTD fromthe fluid based on the characterized temperature change.
 16. The systemof claim 15, wherein characterizing the temperature change of the atleast one RTD over time comprises fitting the temperature data over timeto a function, and wherein a fitting parameter of the function isrepresentative of the degree of deposit on the surface of the at leastone RTD.
 17. The system of claim 16, wherein function comprises anexponential function.
 18. The system of claim 17, wherein the fittingfunction comprises a double exponential function having a first part anda second part, and wherein the first part of the double exponentialfunction represents heat conducted from the at least one RTD to thefluid sample; the second part of the double exponential functionrepresents heat conducted from the at least one RTD to other systemcomponents; and the fitting parameter representative of the degree ofdeposit is present in the first part of the double exponential functionand not in the second part of the double exponential function.
 19. Thesystem of claim 15, wherein the at least one RTD comprises a pluralityof RTDs, and wherein controller is configured to maintain at least oneof the plurality of RTDs at a characterization temperature to inducedeposit onto the surface of the RTD.
 20. The system of claim 19, whereinthe measurement circuit comprises a multiplexer and a demultiplexer incommunication with each of the plurality of RTDs, and wherein themultiplexer and demultiplexer are used to measure the temperature ofeach of the plurality of RTDs one at a time.